Is biofilm formation a critical step for the valorisation of plastic waste ?

Abstract

In the past decades plastic production has increased dramatically and its accumulation leads to great impacts on the environment and human health, which have become issues of global concern. Biodegradation has been suggested as a promising solution in the future in terms of plastic waste management. Some microorganisms are able to generate biodegradable plastics and therefore the use of plastic waste as a carbon source for those microorganisms would achieve the upcycling of the plastic waste and their integration in a circular economy system. Biofilm have been proved to be involved in surfaces biodegradation and may have an important role to play in the context presented. Bacillus amyloliquefaciens, which is known to be a plastic degrading strain, was studied, and in particular its mutant GA1 was chosen given its particular ability to form biofilms. The dynamics of the biofilm formation and maturation was studied to get a better understanding of the biofilm development over a given surface. The biofilm growth was performed using a drip flow bioreactor and the working conditions were optimized in order to promote the biofilm growth and achieve repeatable results between the different reactor chambers and between different experiments. Also the ability of Bacillus amyloliquefaciens GA1 biofilm to degrade poly(ethylene terephthalate) (PET) was tested. In conclusion, the drip flow bioreactor is a powerful tool for the study of biofilms, thanks to its six different culture chambers and low variability between cultivated biofilms. The dynamic study of Bacillus amyloliquefaciens GA1 biofilms shows that the biofilm reaches its maturity after 40 hours of culture which causes significant physiological changes that influence its physical and biochemical properties. Furthermore, the biofilm growth over a PET surface appears to impact the PET surface. Observations using a scattering electron microscope (SEM) indicate that the formation of biofilm on a PET surface has an impact on the integrity of the surface.